1. Field of Invention
The present invention relates generally to the formation of devices which include circuit boards and components which are to be coupled to the circuit boards. More particularly, the present invention relates to systems and methods for improving the consistency of connections between contacts on a circuit board and contacts on a component that is interfaced with the circuit board.
2. Description of the Related Art
Many devices, e.g., non-volatile memory systems such as flash memory cards, include printed circuit boards on which various electronic components may be soldered. Such circuit boards generally allow interconnections to be made between the components, e.g., semiconductor packages and input/output connectors. Typically, such interconnections may be made through electrical contact pads which are present on both circuit boards and components. FIG. 1 is a representation of a circuit board and a semiconductor package which are arranged to make electrical contact through contract pads. A circuit board 140 includes a pattern or an array of contact pads 144 which are generally covered with, e.g., “printed” with, solder paste. Contact pads 144 are coupled to electronic circuitry or traces on circuit board 144. A semiconductor package 150 includes a pattern or an array of contact pads 154 which are often plated with gold or a similar material. Like contact pads 144, contact pads 154 are typically coupled to circuitry or traces associated with semiconductor package 150. Both contact pads 144 and contact pads 154 are arranged to enable signals to be read from or provided to circuit board 140 and semiconductor package 150, respectively.
When semiconductor package 150 is to be soldered to circuit board 140, contact pads 154 may be aligned with contact pads 144. The aligning of contact pads 154 with contact pads 144 is possible when the pattern and the spacing associated with contact pads 154 matches the pattern and the spacing of contact pads 144 of the circuit board 140. Once contact pads 154 and contact pads 144 are aligned, the solder paste on contact pads 144 may be heated, and electrical connections may be made between contact pads 154 and contact pads 144 when the solder paste effectively bonds contact pads 154 to corresponding contact pads 144. That is, contact pads 154 are aligned with contact pads 144 and soldered such that contact pad 154a is in electrical contact with contact pad 144a, and contact pad 154b is in electrical contact with contact pad 144b. 
In general, as described above, contact pads 154 are substantially coated or printed with solder paste. FIG. 2a is a diagrammatic side-view representation of a circuit board or a substrate with contact pads. A circuit board 200 is formed to include pads 204 on at least a top surface of circuit board 200. For ease of illustration, features such as various layers and interconnects associated with circuit board 200 have not been shown. Each pad 204 on circuit board 200 typically includes a layer of solder paste 208, as previously mentioned.
When a component with a contact pad, e.g., component 210 with contact pad 214 as shown in FIG. 2b, is to be electrically coupled to circuit board 200, component 210 is positioned over circuit board 200 such that pad 214 is effectively lined up with an appropriate pad 204, e.g., pad 204a. Once pad 214 is properly aligned with pad 204a, pad 214 may be brought into contact with solder paste layer 208a, as shown in FIG. 2c. When solder paste layer 208a is heated, an electrical coupling may be achieved between pad 214 and pad 204a through solder paste layer 208a. 
The thickness of solder paste layer 208 is relatively difficult to control once solder paste has been heated to effectively bond pads 204, 214. In particular, when there are multiple pads 204, 214 which are to be interfaced, controlling the thickness of solder paste layer 208, e.g., the thickness of the spacing between pad 214 and pad 204a, may be difficult. Typically, reliability issues associated with the performance of circuit board 200 may arise when the spacing between pads 204, 214 is not carefully controlled.
FIG. 2d is a diagrammatic side-view representation of circuit board 200 and component 210 when the spacing between contact pads 204, 214 is relatively large. When pad 214 is spaced too far from pad 204a, solder paste layer 208a′ may be relatively thick, but less dense. As a result, the “joint” formed by solder paste layer 208a′ may crack, thereby compromising the electrical connectivity between pad 214 and pad 204a. While the electrical connectivity between pad 214 and pad 204a may not be compromised by the relatively large thickness of solder paste layer 208a′, the integrity of connections between other pads (not shown) on component 210 and pads 204 may be compromised. For example, the spacing between some pads or pins of component 210 and pads 204 may be such that some pads are effectively “open.” In other words, when the spacing between pads of component 210 and pads 204 is too great, then a solder paste layer 208 may not be able to successfully bridge the distance between pads of component 210 and pads 204. As such, there may either be no connection or an inconsistent connection between pads of component 210 and pads 204.
FIG. 2e is a diagrammatic side-view representation of circuit board 200 and component 210 when the spacing between contact pads 204a, 214 is such that solder paste layer 208a does not effectively join contact pads 204a, 214. When contact pad 214 is spaced too far apart from contact pad 204a, solder paste layer 208a″ may be ineffective for bridging the distance between contact pads 204a, 214. As such, there may be no electrical contact of pads 204a, 214 through solder paste layer 208a″. Specifically, when the distance between contact pads 204a, 214 is too great, then open contacts may occur, i.e., there may effectively be no electrical connectivity between pads 204a, 214.
While spacing pad 204a too far apart from pad 214 to the extent that solder paste layer 208a is thicker than desired or forms an incomplete joint may be undesirable, spacing pad 204a too close to pad 214 may also be undesirable. As shown in FIG. 2f, a solder paste layer 208a′″ may for a relatively thin connection between pad 204a and pad 214. When solder paste layer 208a′″ is too thin, the strength of the joint formed by solder paste layer 208a′″ may be relatively weak. In other words, when the thickness of solder paste layer 208a′″ relatively small, although electrical connectivity between pad 204a and pad 214 may be achieved, the strength of the connection may be compromised. By way of example, when the thickness of solder paste layer 208a′″ between pad 204a and pad 214 is approximately zero millimeters, there is substantially no strength in the joint created by solder paste layer 208a′″. 
Maintaining consistency between connections formed between various pads, leads, or contacts of a circuit board and components of the circuit board is often difficult because controlling the thickness of the space between two pads which are to be electrically connected is not an easy task. Even when the space between two particular pads is acceptable, the space between two other pads may be unacceptable, as it is difficult to maintain a consistent spacing between each pad of a component and corresponding pads of a circuit board within an assembly. Any failure to create and to maintain a desired amount of space between pads and, hence, a consistent thickness of solder paste material intended to fill the space, often compromises the overall integrity of any device which includes the assembly
The reliability of connections formed between pads, leads, or contacts of a circuit board and components of the circuit board is important to ensure that a device which includes the circuit board may meet performance standards. When connections are not reliable, signals that are to be passed through the connections may not be successfully routed. As discussed above, unreliable connections or bridges between pads may include open connections and weak connections. The presence of even a single unreliable connection within a device may greatly affect the performance of the device.
Therefore, what is needed is a method and an apparatus for improving the integrity of connections between a circuit board and components of the circuit board. That is, what is desired is a method and a system which enables the thickness of a solder paste layer which bonds pads of a component with pads of a circuit board to effectively be controlled.